A BATTLE IS BREWING

The first salvos in the root beer war already have been fired. Jon Harris, a spokesman for Somers, N.Y.-based Pepsi-Cola Co., said Pepsi launched its first commercials for its Mug line of root beer, diet root beer, cream and diet cream sodas last month with a series of commercials centering around a new "The Foam Goes Straight to Your Brain" campaign."We're trying to introduce root beer to a new,

The first salvos in the root beer war already have been fired. Jon Harris, a spokesman for Somers, N.Y.-based Pepsi-Cola Co., said Pepsi launched its first commercials for its Mug line of root beer, diet root beer, cream and diet cream sodas last month with a series of commercials centering around a new "The Foam Goes Straight to Your Brain" campaign.